Nice idea in theory, except that now you have a system that immediately and catastrophically breaks if there is ever a backend outage (due to, say, a cyberattack or incompetent software trying to prevent one) or your reader loses network connectivity.

> you should never do a system with stored value on a smart card

...if you can afford to ignore the disadvantages of not doing it. Quite often, you think you can, until you can't.